Hello there -
Yes, you have observed correctly. Generally speaking, Green amongst a few others from the golden era (55-65 in my opinion) are very difficult to come by, especially in good condition. Green sparkle is my absolute favorite when it comes to slingerland, and I am a bit obsessive about it.
I have never found any information pertaining to why they are so scarce - generally, the most popular colors for slingerland drums during this time period were Red and Blue sparkle, with Silver following. Aside from these 3 sparkle colors, White Marine Pearl always remained a front runner due to it's association with Gene and Buddy. I believe Black Diamond Pearl was also popular, just a bit less than the aforementioned wrap options. If I had to guess at the popularity of wraps in order, I might say:
-WMP
-Blue
-Red
-Silver
-Black Diamond Pearl
-Gold Sparkle
-Sparkling Pink Champagne
-Duco color options - particularly Blue on Blue
Black Sparkle Pearl
-Light Blue Pearl (commonly known as sky blue pearl, the ludwig name for this finish)
Any other finishes from this era I consider very uncommon and rare to find. That would include (in no order):
Oyster Pink Pearl
Blue Ripple Pearl
Capri Pearl
Gold Veiled Ebony Pearl
Sparkling Pink Pearl
Sparkling Green Pearl
Fiesta Pearl
Mardi Gras Pearl
Sparkling Peacock Pearl
Turqoise Veiled Pearl (not listed in catalog)
This is all my opinion which has been developed over a number of years - I am a slingerland-only drummer (with a few exceptions) and so I have followed and paid close attention to the market for the last decade and then some.
I would say for each of the rare finishes listed below, I have only see them appear on the internet a handful of times. I have never seen a complete set of drums in peacock pearl - only a snare drum.
Green was simply not a popular color during the time period. When you do find it, it is commonly found on Marching Percussion instruments from this era as a banded wrap, matched with an additional color.
The only slingerland's I own in original green sparkle are snare drums. My crown ***el is my 1951 Slingerland Radio King in original Green Sparkle - it is my most expensive snare drum purchase to date, costing me just under $1k.
I would say I have seen less than 15-20 snare drums in original green sparkle go up for sale in the last 10 years. Often times they are only for sale for a few hours, unless they are grossly overpriced.
I hope you don't mind my indulgence - this is a favorite niche of mine in this drum collecting hobby. I'm a bit obsessive when it comes to green sparkle!
Cheers, everyone.